A fundamental question I am sure. But why do PA speaker makers make Trapiezoidal caps? Why not rectanglular? If its a resinance thing, surely the rear face should be angled as well?
1 reason or atleast 1 marketing pitch of a design feature:
So that they can be used on their side as a monitor or floor projection speaker. The pair we use for live sound says that on the brochure.
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Danny
So that they can be used on their side as a monitor or floor projection speaker. The pair we use for live sound says that on the brochure.
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Danny
You have to remember...
.. that in a small situation you would be using maybe 1 speaker per side.
However, in larger situations there are often many speakers, and one of the best ways to arrange them for spread of sound is in a arc (both vertically and horizontally), which is much easier if you have a trapezoidal shape.
Remember, these are mass produced, so they make one shape that will be useful in many situations, rather than go to the extra cost of having rectangular ones and trapezoidal ones.
There may also be issues with internal resonances, but I think you will find that those are of secondary importance in the design brief.
.. that in a small situation you would be using maybe 1 speaker per side.
However, in larger situations there are often many speakers, and one of the best ways to arrange them for spread of sound is in a arc (both vertically and horizontally), which is much easier if you have a trapezoidal shape.
Remember, these are mass produced, so they make one shape that will be useful in many situations, rather than go to the extra cost of having rectangular ones and trapezoidal ones.
There may also be issues with internal resonances, but I think you will find that those are of secondary importance in the design brief.
The main reason is indeed marketing. When bands started using multiple PA boxes for more power they also usually placed them side by side, for the sake of convenience and in the mistaken belief that speakers placed side by side resulted in better horizontal dispersion, though the opposite is true. They also aimed them at angles in attempts to further broaden the horizontal dispersion, also completely wrong, but back in the 1970's who knew? Well, the manufacturers for the most part did, but they wanted to sell speakers, not educate roadies in the audio arts.
This placement resulted in the cabinet fronts being separated, which is ugly, so someone came up with the bright idea of trapezoidal boxes to allow cabs to be horizontally splayed while maintaining a solid face to the array. This does serve a sonic purpose at lower frequencies, but still was more an attempt at making so-called cluster arrays visually more appealing, and was a great marketing tool to get everyone to dump their rectangular speakers for trapezoidal speakers. Even reputable manufacturers that knew better jumped on the trapezoidal bandwagon, as business is business after all.
But eventually roadies started reading books on audio acoustics and learned that speakers should always be stacked vertically, and thus the vertical line array was born. Reborn, actually, as the PA columns from as far back as the '40s were technically correct but losers in the marketplace because they didn't look 'right'.
This placement resulted in the cabinet fronts being separated, which is ugly, so someone came up with the bright idea of trapezoidal boxes to allow cabs to be horizontally splayed while maintaining a solid face to the array. This does serve a sonic purpose at lower frequencies, but still was more an attempt at making so-called cluster arrays visually more appealing, and was a great marketing tool to get everyone to dump their rectangular speakers for trapezoidal speakers. Even reputable manufacturers that knew better jumped on the trapezoidal bandwagon, as business is business after all.
But eventually roadies started reading books on audio acoustics and learned that speakers should always be stacked vertically, and thus the vertical line array was born. Reborn, actually, as the PA columns from as far back as the '40s were technically correct but losers in the marketplace because they didn't look 'right'.
Yet another reason to be sceptical when faced with statements like "you couldn't design a speaker of the same quality as the big companies because they spend so much on research" If they USED their knowledge they'd build simple, cheaper shapes ( or save the complex stuff for the inside).
A plastic mold is a plastic mold...
... I don't think a rectangular plastic mold would be much cheaper than a trapezoidal one. note also all the rounded corners etc, handles post holes etc that they mold into the cabinet. They are built as a multi-function unit !!
The DIY just doesn't have access to that sort of molding facility or plastic types....
Note... I am NOT saying DIY can't make something that sounds as good! only that we can't easily do that type of cabinet
... I don't think a rectangular plastic mold would be much cheaper than a trapezoidal one. note also all the rounded corners etc, handles post holes etc that they mold into the cabinet. They are built as a multi-function unit !!
The DIY just doesn't have access to that sort of molding facility or plastic types....
Note... I am NOT saying DIY can't make something that sounds as good! only that we can't easily do that type of cabinet
I was really thinking about the acoustic properties of a shape. According to our more learned posters, the shape is a marketing issue. My post works for wooden cabs.
The plastic cabinet is an interesting point. From my limited knowledge, it needs a 4 deg angle to get the thing out of a mould so rectanglular is MORE expencive. The handles add complexity so you need a multipart tool. You would need to be making thousands before you paid back the moulding cost.
In this case the way plastic is incorperated into the design is probably a finantial choice not accoustic although it would allow some interesting air-flow/resonance possibilities. Infact it NEEDS curves to add rigidity.
However I don't know about you, but I can HEAR plastic so I don't think this clever design happens in practice. I guess they just build what sells huh?
The plastic cabinet is an interesting point. From my limited knowledge, it needs a 4 deg angle to get the thing out of a mould so rectanglular is MORE expencive. The handles add complexity so you need a multipart tool. You would need to be making thousands before you paid back the moulding cost.
In this case the way plastic is incorperated into the design is probably a finantial choice not accoustic although it would allow some interesting air-flow/resonance possibilities. Infact it NEEDS curves to add rigidity.
However I don't know about you, but I can HEAR plastic so I don't think this clever design happens in practice. I guess they just build what sells huh?
Meyer.....
.. who of course know nothing about sound !!!
A large number of their speakers are designed as Trapezoidals, and are made of ply outer.
They are designed that way so they can be more easily used in horizontal spread arrays.
Here is an eg.. read the stuff down the bottom, where they actually give spread and spl of different set-ups.
http://www.meyersound.com/products/concertseries/ds-2p/pdfs/ds-2p_oi.pdf
In this eg the horizontal array is actually used to narrow the spread while increasing spl. but other speakers in their rangecan be used to widen the spread.
search through their web site, do some reading, look at their "Concert" range.. nearly all trapezoidal, draw your own conclusions !!!
Sure its a marketing feature, but based purely on functionality !
.. who of course know nothing about sound !!!
A large number of their speakers are designed as Trapezoidals, and are made of ply outer.
They are designed that way so they can be more easily used in horizontal spread arrays.
Here is an eg.. read the stuff down the bottom, where they actually give spread and spl of different set-ups.
http://www.meyersound.com/products/concertseries/ds-2p/pdfs/ds-2p_oi.pdf
In this eg the horizontal array is actually used to narrow the spread while increasing spl. but other speakers in their rangecan be used to widen the spread.
search through their web site, do some reading, look at their "Concert" range.. nearly all trapezoidal, draw your own conclusions !!!
Sure its a marketing feature, but based purely on functionality !
Andy, Meyer certainly knows about sound, but they know more about marketing and doing what it takes to stay in business. The narrowing of the spread is not going to eliminate 1/2 wave cancellation at any frequency where the span between the radiating planes exceeds a wavelength, and that pretty much encompasses the entire HF spectrum. One can state unequivocally that there is no functionality in placing mid or high frequency elements on a horizontal plane, but Meyer and every other manufacturer was not going to lose sales by not providing what the consumer wanted.
Today's new generation of educated roadies have abandoned the cluster array in favor of what actually works, and by the way, Meyers line array is sweet. But they wouldn't be building them if there wasn't a market for them. Technology does not drive the marketplace; it is the marketplace that drives technology.
Today's new generation of educated roadies have abandoned the cluster array in favor of what actually works, and by the way, Meyers line array is sweet. But they wouldn't be building them if there wasn't a market for them. Technology does not drive the marketplace; it is the marketplace that drives technology.
The fact remains.....
.. that they are built as trapeziums so they can be more easily combined in a horizontal array. Be that good or bad, acoustically functional or not......, that is the main reason they are trapezoidal !!!!
being able to better angle speakers when next to wall, may also be a reason.
.. that they are built as trapeziums so they can be more easily combined in a horizontal array. Be that good or bad, acoustically functional or not......, that is the main reason they are trapezoidal !!!!
being able to better angle speakers when next to wall, may also be a reason.
Flown line arrays?
Just out of curiosity, any reason why flown line arrays tend to be curved back at the bottom instead of hanging straight down all the way down?
Just out of curiosity, any reason why flown line arrays tend to be curved back at the bottom instead of hanging straight down all the way down?
That sort of array
you will notice, is usually fairly high above the audience. I think its that the top section is aimed at the crowd further out from the stage, the lower section is aimed more at the crowd closer to the stage. because the near stage ones are so much closer, there needs to be fewer of them.
you will notice, is usually fairly high above the audience. I think its that the top section is aimed at the crowd further out from the stage, the lower section is aimed more at the crowd closer to the stage. because the near stage ones are so much closer, there needs to be fewer of them.
Lime arrays have very small vertical dispersion angles, less than 5 degrees off axis with large arrays, so the lower elements have to be aimed at the coverage zone or the sound would simply travel over the heads of the audience. More elements are aimed straight out for the reason Andy surmised, though there isn't much difference in close versus far levels as large line arrays roll off SPL at a 3dB per doubling of distance instead of 6dB.
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